The Study On Effects Of Fatigue Damage Upon Trabecular Bone By Numerical Simulation

Fatigue damage in bone occurs as a result of daily loading activities and is considered as one of the most important components of mechanical stimuli to activate bone remodeling process. Our objective is to develop a new remodeling model which incorporates strain-adaptive and damage-induced remodeling algorithms and to investigate the changes in morphology of trabeculer bone and vertebra via computer simulation.A new mathematical mechano-regulatory model relating the density change rate with both mechanical stimuli has been developed. According to the state of damage existing in bone, the model was divided into two parts. Below a critical damage rate threshold, strain-adaptive remodeling algorithms were adopted. Above the critical value, damage-induced remodeling algorithms were used, which involve a biological process of occurrence/repair of stochastic microdamage based on the Basic Multicellular Units (BMUs). Finally, the model was applied to a two-dimensional simulated trabecular bone and vertebra based on Finite Element Method.The simulation results showed that bone microstructure became fragile with the loss of trabeculae and over time emerged anisotropic configuration. The vertical trabeculae can be preserved during the simulation, but the horizontal ones lost more. It was found that the elastic modulus of vertical direction retained unchanged but that of horizontal ones decreased, indicating that the changes in elastic modulus of trabecular structure was highly correlated with the integrality of trabeculae. The results simulated were consistent with the clinical observations.The results of this study suggest that trabecluar bone deteriorates inevitably with natural aging, and that the anisotropic configuration enables bone to adapt to compression loading rather than tension loading. The new remodeling model can help to gain more insights of mechanism of bone loss and identify improved treatment and prevention for osteoporosis or stress fracture, and can provide a quantitative computational framework to investigate the influence of fatigue damage on the trabecular bone and vertebra morphology.